1. Field of the Invention
This invention relates to the preparation of lubricating oil compositions containing overbased metal naphthenates.
2. Description of the Prior Art
Overbased metal salts of organic acids which contain an amount of metal in excess of that theoretically required to replace the acidic hydrogen atoms of the acids have found utlity as components of lubricating oil composition. These salts impart to the lubricating compositions an alkaline reserve which neutralizes sulfur containing and other acids formed during combustion of the fuel thereby reducing corrosion of the engine and decreasing wear of piston rings and cylinders.
Various methods for producing metal naphthenates are already known such as those described in U.S. Pat. Nos. 2,938,828; 2,865,956 and Japanese Pat. Nos. 48,094,814; 48,084,815 and 49,010,906.
Although these prior art methods can produce highly overbased metal naphthenate lube oil compositions, they often have the drawback of having relatively slow filtration rates thereby requiring costly and extensive filtration apparatus in order to obtain any meaningful production. Filtration of the final overbased naphthenate lube oil composition is normally necessary since customers require a clear solution and the product in a crude state often contains considerable solids predominantly undispersable, agglomerated calcium carbonate particles which require removal.